ALFA75 error light

My friend buy a -91 alfa75 twinspark .

it has some problem ,
when accelerate ,it is cut -off (like rpm cut-off) at 3500-4000 rpm !
ecu,rpm sensor,tps sensor,air vane (air sensor) all the changed .

I know but I dont remember well,
this motronic 4.1 ecu has error code light out pin .

one time Im check a alfa 33 1.7 ecu out ,
one led connect and when open the ignition ,it give an error codes with flashes ..

do you any one know, how?

also we have alfaromeo tester but no any alfa75 catrige ..